As a kind of medium and long wave infrared optical material, elemental ZnS has excellent optical and mechanical properties. At present, the development of hypersonic vehicle urgently requires research on the hightemperature performance of elemental ZnS infrared windows.The hightemperature performance of elemental ZnS at different temperatures were studied in this paper, and the results show that the emissivity of elemental ZnS increases with the increase of wavelength, and increases with the increase of temperature at the same wavelength. At 500 ℃, the average normal optical spectrum emissivity is less than 0.05 at 3～5.5 μm, and less than 0.10 at 7～10.5 μm. In the range of 2～9.5 μm, the temperature has little effect on the transmittance, but after 9.5 μm, the transmittance decreases significantly as the temperature increases. The refractive index, thermal optical coefficient, and expansion coefficient increase with increasing temperature. Temperature has almost no effect on bending strength. The elastic modulus decreases with increasing temperature, the elastic modulus at 800 ℃ decreases by about 30% compared to that at room temperature.